The present invention relates to a driver for attaching a multiple sprocket arrangement having a plurality of sprockets with different numbers of teeth to a rear axle of a bicycle. The present invention relates in particular to a driver that is attachable to the sprocket assembly in a torque-transmitting manner, and an adapter, which may be coupled to the driver, wherein the sprocket assembly may also include sprockets having a smaller inner diameter or dedendum circle than the outer diameter of the driver, and wherein the sprocket assembly in the region of the sprockets with smaller diameter may be connected to the driver via the adapter.
Various systems are known in the prior art for the attachment of multiple sprocket arrangements to rear axles. Typically, a driver is supported in a rotatable manner on the rear axle of a bicycle via a bearing arrangement. The driver is in torque-transmitting engagement with the hub shell via a one-way clutch and permits a torque transmission in the one direction of rotation (drive direction), whereas it is decoupled from the hub shell with respect to rotation in other direction in order to provide a freewheel. Typically, an outer circumferential surface of the driver is provided with a splined configuration or a similar profile in order to allow individual sprockets, or an assembly composed of several sprockets, to be mounted thereon so as to transmit torque. A solution of this type is shown in the prior art, for example, in DE 199 15 436 A1. Comparable solutions are further shown in documents JP 59-165293, GB 2 177 628 A or EP 0 277 576 A2.
Another known solution is described in EP 1 342 657 B1. It discloses a possibility of attaching sprockets with a smaller diameter to a driver. Although this system is widely used, it is increasingly reaching its limits and has some disadvantages. For example, the number of sprockets is continually increasing, particularly on high-end bicycle shifting systems now being used by both professional cyclists and recreational cyclists. Here both relatively large increments, but also especially relatively small increments are often being used so as to provide, for example, the optimal gear ratio when covering flat terrain or when riding in a group at a constant cadence. In both cases, i.e., whenever small increments with small jumps in gearing are provided, or whenever large jumps in gearing need to be available, there is an increasing need for very small sprockets, i.e. sprockets with 10 teeth or less. Such small sprockets, however, cannot be mounted on a driver of the conventional type, and thus resulting in additional parts being necessary which have a complicated structure or are difficult to install. Small-diameter sprockets specifically require relatively complex carrier profiles. Overall, particularly with the adapter solution shown in the prior art, the problem arises that a multiplicity of different parts is necessary, which are complicated to install and entail a relatively heavy weight.
Another disadvantage of this solution from the prior art is that the multi-part arrangement requires the outer bearing be further inward than the driver in the axial direction. This means that when the bicycle chain engages the smallest sprocket, there is a relatively large axial distance between the location of the chain engagement and the location of torque transmission and the bearing. This results in undesirable mechanical stresses and a less-effective power flow.